Although warning light assemblies for emergency vehicles are used in many types of situations, one of the most common uses is to provide an effective warning for the vehicles as they approach traffic intersections. Despite the use of warning light assemblies in this situation, often accompanied by the use of sirens, collisions at intersections remain a serious problem for emergency vehicles.
With the increasing popularity of air conditioning and stereo systems in vehicles, sirens are often not heard. The sound of conditioned air through the ducting of a vehicle coupled with a loud stereo often means that an emergency vehicle is not identified until its warning lights are noticed. As air conditioning and audio systems in vehicles proliferate, it is important to maximize the ability of warning lights for emergency vehicles to warn other vehicles of their approach, particularly at intersections.
Traditionally, warning light assemblies for an emergency vehicle have been mounted on a base that traverses a roof of the vehicle. The warning lights are distributed substantially in a row across the roof and are enclosed by one or more transparent domes that protect the lights from the elements of the ambient environment. To draw attention to the lights, their intensities are varied, usually either by flashing them or focusing the lights into beams that rotate.
The visual effect of these flashing and/or rotating warning lights is greatest when viewed from directly in front or behind the vehicle. At intersections, however, the greatest danger of collision is derived from approaching vehicles in a crossing street or highway. These vehicles view the row of warning lights on the emergency vehicle at angles up to approximately 90.degree. to the heading of the emergency vehicle. At such angles, the profile of the lights is effectively narrowed, thereby reducing their visibility. Furthermore, the domes over the warning lights are often configured such that their transmittance at angles approaching 90.degree. is significantly less than when the warning lights are viewed from directly in front of or behind the vehicle. The combination of the reduced profile and transmittance seriously compromises the warning ability of the lights for vehicles approaching the emergency vehicle from a side angle, as is typically in an intersection.